Method of making can bodies



April 27 1937. H, SEBELLL 2,078,546

METHOD OF MAKING CAN BODTES Filed April 11, 1934 Fig.1.

Harry Sebe H b mmwjmm ATTys.

Patented Apr. 27, 1937 UNITED STATES PATENT OFFICE and mesne assignments, to Crown Cork & Seal Company, Inc., Baltimore, Md., a. corporation of New York Application April 11, 1934, Serial No. 720,049

3 Claims.

This invention relates to the making of can bodies of the type which are formed from a blank of sheet metal that is bent into the proper shape and has its meeting edges secured together thereby forming a side seam which extends from the top to the bottom of the can body.

One object of the present invention is to provide an improved method of making a can body of this type by which the can body is formed by welding or fusing together the two meeting edges of the blank and in so doing producing a can body in which the side wall has no greater thickness at the side seam than at other portions of the can.

In making a can body it is desirable that the side seam should be so formed that there will not be an edge of the sheet metal exposed on the interior of the can, for when the can is used for the packaging of food products, such as canned corn, canned peas, and other canned vegetables, or canned .fish and the like, the presence of a raw edge of the sheet material of which the can is made on the interior of the can will have a deleterious effect on the food products. In order to produce a can which is free from the presence of such raw edges it has been the common practice to make the side seam of the can by providing each of the meeting edges of the sheet metal blank with a hook portion which interlocks with the hook portion of the other edge and then soldering such hook portions together in some appropriate way, one way being that illustrated in my Patent No. 1,888,413, November 22, 1932 or in my Patent No. 1,918,197, July 11, 1933. A side seam having the construction shown in said patents does not have any raw or cut edge of the sheet metal exposed on the inside of the can, but it has the disadvantage that there will be several thicknesses of sheet metal along the line of the seam, the presence of which extra thickness at this point is detrimental when it comes to the operation of flanging or otherwise shaping the can body for the reception of the can end.

In order to reduce the thickness of the can body at the ends of the seam it has heretofore been customary to notch the blank at the corners so that when the side seam, such as shown in the above-mentioned patents, is formed, the can will have only a double thickness at the extreme ends of the seam. But even this double thickness results in more or less dlfliculty in properly flanging or deforming the can body for the attachment of the can ends.

One of the objects of my invention is to provide an improved method of making a can body which will be entirely free from any cut edge on its interior and which is so made that the side wall has no greater thickness at the seam than at other portions. As stated above this object is secured by fusing or welding together the two meeting edges of the can blank.

The tin cans for packaging food and other products are made from sheet iron which is tinned, and in order to weld together properly the meeting edges of the blank it is desirable to detin such meeting edges. Where this is done the can body formed by welding the meeting edges of the blank together will have a zone extending along the seam from which the coating of tin has been removed.

Another feature of my invention relates to a novel method of and apparatus for retinning this zone so that when the can is completed it will be entirely tinned both inside and outside and at the same time will have a seam which is not appreciably thicker than the thickness of the sheet metal of which the can is made.

In order to give an understanding of the invention I have illustrated in the drawingsomewhat diagramatically an apparatus embodying my invention and by which the process may be carried out.

In the drawing, Fig. 1 is a view of a blank of sheet metal from which the can body is to be made, the opposite edges of said blank having been de-tinned;

Fig. 2 shows the blank bent into approximately the shape of the can body;

Fig. 3 is a sectional view showing the operation of welding or fusing the meeting edges of the can body together;

Fig. 4 is a section on the line 4-4, Fig. 3;

Fig, 5 is a diagrammatic sectional view illustrating the steps of fusing the meeting edges of the can together, cleaning the joint thus made, and retinning the can along such joint;

Fig. 6 is a perspective view of a can body made in accordance with my invention.

In the drawing l indicates a blank of sheet metal from which the can body is made. This sheet metal is of the kind usually used in the manufacture of tin cans for packaging food, that is, it is sheet metal which is provided on both surfaces with a coating of tin; This blank is bent into the shape of the can body to be made, thereby bringing the opposite edges 2, 3 together and, as stated above, said edges are permanently secured together by being fused or welded together. In order to permit this to be done it is desirable to remove the tin coating from the marginal portions of the blank along the edges 2 and 8. This may be done in any suitable way, as for instance by abrasion or by heat or by chemical action, and when the tin has been thus removed the blank will have on its ends two marginal zones 4 and 8 along the edges 2, 8 which are free from the tin coating. The blank I is then bent into the shape of the can body to be made as shown in Fig. 2 so as to bring the edges 2 and 8 into meeting relation, and in thus bending the blank the edge portions 2 and 8 are bent inwardly slightly as shown at 8. The detinned marginal portions 4 and 8 of the formed blank are then brought into overlapping relation as shown in Fig. 3 and are welded or fused together. This can conveniently be done by bending the blank around a mandrel or supporting member I which is of a size and shape corresponding to the interior dimension-of the can and which has welding electrodes associated therewith.

In placing the can body around the mandrel or support I preparatory to the fusing or welding operation it is desirable that the detinned marginal portions 4 and 5 should be brought into overlapping relation and this is herein provided for by the employment of two wings 8, 8 which are pivotally connected at 68 and are adapted to embrace the formed can blank and close it onto the supporting member I. When the blank formed as shown in Fig. 2 is first placed on the horn or supporting member I it will have substantially the dotted line position shown in Fig. 3, the bent portions 8 thereof standing slightly away from the horn.

If the can body is placed between the supporting member I and wing members 8 and 8 when in their separated relation as shown by dotted lines, Fig. 3, and subsequently the wing members are moved toward each other into the full line position, the ends ID of these wing members 8 and 8 will engage the formed can blank adjacent the meeting edges where it stands up away from the horn I as shown by dotted lines in Fig. 3 and will close said edges together and press them together in the overlapping relation shown. When in this relation the overlapping portions are the detinned portions of the can blank.

While the can blank is thus held with the detinned portions in overlapping relation, such overlapping portions are passed between the welding electrodes which results in fusing the metal along the seam and thus integrally uniting the meeting edges, and in doing this the double thickness of sheet metal is subjected to pressure so as to produce a welded or fused seam having substantially the same thickness as the sheet metal.

One of the welding electrodes is placed within the mandrel or support I and the other is located outside of the mandrel. The electrode within the horn or mandrel is shown at H and it is mounted in a chamber I2 which extends longitudinally of the horn or support. The electrode on the exterior of the horn is indicated at l3. Each electrode is preferably in the form of a roll, the interior electrode or roll I I being mountwhich current is delivered to the electrodes. The wire I! is connected to a wiring terminal 2| secured to the bearing i1 and said terminal carries a brush 22 which engages with a cylindrical hub portion 28 of the electrode i3. The wire 28 is located in the channel or chamber l2 and it leads to a wiring terminal 24 carried by a support 28 of insulating material which is secured to the side wall of the chamber l2. This support 28 is provided with a brush 26 engaging the cylindrical hub portion 21 of the electrode ll.

As the formed can blank with its detinned edge portions 4 and 5 overlapping as shown in Fig. 3 is moved along the horn or support I with the overlapping edges passing between the electrodes, such edges will be fused or melted and thus welded or integrally united, and in the performance of this operation the double thickness produced by the overlapping relation will be reduced to a single thickness by the pressure of the electrodes thereby producing a can in which the meeting edges are integrally united.

In order to finish the can so that it is suit able for packaging food it is necessary to retin the joint or the detinned portions. To provide for this it is also desirable first to smooth up the surface of the can along the seam because the welding operation is liable to leave a surface which is more or less rough. For this purpose I have provided two finishing rolls 28, 29 which are preferably of an abrasive nature and between which the welded portion of the can body passes as it is moved along the support ing member I. These abrasive rolls 28, 28 are preferably driven so that they will have a grinding or smoothing action on both the interior and exterior surface of the can body.

The abrasive roll 28 is mounted on a shaft 88 supported by the walls of the chamber l2 and it has fast therewith a sprocket wheel 3| over which passes a sprocket chain 82 that extends to any suitable source of power. The abrasive wheel 28 is mounted on a suitable support or shaft 38 and has rigid therewith a sprocket wheel 84 around which passes a power driven sprocket chain 85.

For retlnning the portions of the can body which have been previously detinned it is desirable to first apply an acid to such portions and then to apply the melted tin thereto. For applying the acid or flux to the interior of the can body I have shown a roll 88 situated within the chamber l2 and which dips into a tank 81 carrying the acid or other fluxing material 38. As the can body is moved along the supporting member I this roll engages the interior thereof along the seam and thus applies the necessary flux or acid.

For applying the acid to the, exterior I have shown a tank 38 situated above the horn and having a delivery spout 48 provided with a wick and through which the acid may be delivered to the exterior of the can.

While the actual application of the tin coating may be performed in various ways I have herein shown a device for applying the tin coating to the interior of the can which comprises a tinning wheel 4| supported on a shaft 42 situated in the chamber l2 and dipping into a tank 88 containing a molten tinning material 44. As the can body is moved along the support I this wheel ll engagesthe interior surface thereof and applies the coating of tin to the portion of the surface of the can which has been previously detinned.

The tinning material in the tank 88 may be material will flow down the groove in sufficient I! through which water or some other cooling and rests against the detinned portion of the can body. This iron is provided with a feed groove 48 leading into the tank so that the tinning quantity to perform the requisite tinning operation.

The tinning material in the tank 45 may be kept in a molten state in any approved way.

when the completed-can body, which is shown at 50, Fig. 6, is removed from the supporting member I it will have the construction shown in said Fig. 6, that is, it will have a body of substantially uniform thickness throughout in which-the meeting edges .are integrally united and which is completely tinned both on its inside and outside.

In said Fig. 6 the zone between the dotted lines 55 indicates the zone where the seam is formed and which has been retinned inside and outside. A can body having this construction can be fiangedor otherwise deformed for the purpose of producing a can without the disadvantages which result in connection with a can body having a side seam which is thicker than the sheet metal of the can body.

Another advantage which results from this invention is that there is a definite saving of material in the making of the can body.

In order to make a can body of a given size with a side seam such as shown in said Patents No. 1,888,413 and No. 1,918,197 a larger blank, and consequently one having a greater surface area, is requiredthan to make a can in accordance with this invention. This longer blank of greater area is necessary, because of the fact that in forming the seam a sumcient amount of material isrequired to make both hook portions which produces four thicknesses at the seam. With the present invention there is only a slight overlapping of the meeting edges so that for a given size can each blank can be a quarter or threeeighths of an inch shorter than is necessary for making the seam shown in the above-mentioned patents. While this is asmall saving on each can yet it is a saving of importance when the number of cans which are made annually is taken into consideration.

In order to prevent the tinned surface of the can body from becoming'discolored by the heat transmitted to it from the mandrel 'i I propose to provide said mandrel with a cooling chamber medium may be circulated. This cooling chamber is shown as extending around the sides and bottom of the electrode-receiving chamber l2 and it results in maintaining the mandrel sufficiently cool so that the can body will be kept below the temperature at which the tin would become discolored.

Sometimes a can body will be made with some printing thereon or with some special finish and frequently such printing matter or the finish is applied to one face of the blank before it is bent into the form of the can'body. This feature of cooling the mandrel is also of advantage when cans of this type are being made because the mandrel will be kept at a sufliciently low temperature so that the finish on the can body will not be injured by reason of the contact between the can body and the mandrel.

It will be understood, of course, that this invention is applicable to the making of can bodies having any desired cross-sectional shape. illustrative purposes I have shown the invention as applied to the making of a cylindrical can body, in which case the mandrel has a cylindrical shape. If, however, a can body is oval or square or rectangular in cross section, or has any cross-sectional shape, the mandrel will have a corresponding shape.

I claim:

1. The process of making a can body from a tinned blank, which process consists in forming the blank into the shape of the can body with the edges in meeting relation, moving said shaped blank along and in encircling relation with a supporting mandrel, fusing said edges together during movement of the blank along said mandrel and then retinning the can body along the fused seam while said body is moving lengthwise of the mandrel.

2. The process of making a can body from a tinned blank, which process consists in forming the blank into the shape of the can body with the edges in meeting relation, moving said shaped blank along and in encircling relation with a supporting mandrel, fusing said edges together during movement of the blank along said mandrel and then retinning the can body along the fused seam 'on both theinside and outside thereof while the body is moving lengthwise of the mandrel. I

3. The process of making acan body from a tinned blank which consists in forming the blank in the shape of the can body with the edges of For the blank in meeting relation, moving said 

